The summit near Crugmore Farm, now called Banc-y-Warren, is actually only one of a number of possible locations in the area. Topologically it forms a minor summit which is actually lower than the summit a kilometre to the north (seen on this Map obscured by sand extraction workings). This more major summit is a much more likely setting for the traditional top of the mountain, and previously had a distinctively man-made mound on the top (just to the right of where the footpath extending from the word "Sand Pit" reaches a T-junction on the map), along with an entrenchment at Crug Llwyn-Llwyd ["Hillock/Heap/Tumulus of the Grey Bush/Grove"] (just above the word "Sand Pit") just below Banc Cil-maen-llywd ["Bank grey-stone-corner/retreat"]. These can be seen on the 1891 Map here. This is plainly believed to be the site of the wonder by W.Llewelyn Williams*, who notes:
From Cardigan, the archbishop proceeded towards Pont-Stephen, leaving a hill, called Cruc Mawr, on the left hand, which still retains its ancient name, and agrees exactly with the position given to it by Giraldus. On its summit is a tumulus, and some appearance of an intrenchment.
The tumulus appears on the first editions of both the 1:10560 and 1:2500 series Ordnance Survey maps. While it is not marked as a tumulus on either map this is common for these series. By the first revision of both (1:10560: 1888-1914; 1:2500: 1893-1915) it has gone, though not as an obvious result of quarrying. This may be the "Uncertain defended enclosure" indicated for the middle of the sand pit by the RCAHMW*. It is unclear on present maps whether the area has now been mined out. The intrenchment was scraped by quarrying in 1975*.
Whether the mound is the grave mentioned depends on the meaning of the "Crug" in Crug Mawr: "The Big Hillock/Heap/Tumulus". The name is ambiguous as to whether it refers to a hillock or tumulus. It seems unlikely a tumulus would resize to the length of a man, however the Latin uses tumulus specifically, as it does in Wonder 13, as well as sepulcrum (see also this Note from Wonder 13 on the Welsh Thom). The question is really whether "Crug" could refer just to the small conical mound of Banc-y-Warren, or whether it could be the name of the whole mountain, allowing it to cover the area of the tumulus (even, potentially, taking its name from the tumulus in the way that the Carn Gafallt of Wonder 12 is named after a burial mound). The evidence from the sources is equally ambiguous. The modern identification of Banc-y-Warren as Crug Mawr comes from the farm name, and the following quote from Lewis* (online), which includes the parish the hill is located in:
Soon after the death Henry I, a memorable battle was fought near Crûg Mawr, a conical hill in this parish [Llangoedmore], between the Welsh, commanded by Grufydd ab Rhys and the English, in which the latter sustained a signal defeat.
The parish included many areas around and west of Banc-y-Warren
and Kelly's Directory of 1895* for
the parish includes
James, John, farmer; Crugmawr.
Plainly this reference suggests there might be a source in a history manuscript tying the name to the battlesite, with a description of the location. However, this source is not terribly forthcoming (Note). It is likely that the connection actually lies with the following quote from the travels of Gerald of Wales, who wrote just within living memory of the battle (51 years later) *:
We proceeded on our journey from Cilgerran towards Pont-Stephen [Lampeter], leaving Cruc Mawr, i.e. the great hill, near Aberteivi [Cardigan], on our left hand. On this spot Gruffydd, son of Rhys ap Tewdwr, soon after the death of king Henry I., by a furious onset gained a signal victory against the English army, which, by the murder of the illustrious Richard de Clare, near Abergevenny (before related), had lost its leader and chief. A tumulus is to be seen on the summit of the aforesaid hill, and the inhabitants affirm that it will adapt itself to persons of all stature and that if any armour is left there entire in the evening, it will be found, according to vulgar tradition, broken to pieces in the morning.
Gerald is less specific about the location/description, though he does give some useful information - the hill is to his left travelling from Cilgerran to Lampeter. The simplest route between the two is along the line of the current A484, the Cilgerran road following the river northeast to Llechryd before continuing on this lowland route to Newcastle Emlyn and the Lampeter. This route skirts the foothills of the massif which includes Banc-y-Warren and Banc Cil-maen-llywd, however, at this distance the massif itself takes over one's view, expanding the possible locations. The summit of the massif is around Felinwynt, though there is no sign of any burial structures there. In particular, however, a second hill on the massif, now unnamed(?possibly Allt Pencraig ["Ridge at the head of the rock"]) near the intriguingly named Ffynnoncripil, stands "conical" and high above the road, and is topped by a tumulus (actually two**). However, it is equally possible Gerald just mistook Banc-y-Warren for a tumulus, or reported a confused account. In short, it is difficult to be conclusive: Banc-y-Warren is certainly conical and on the kind of major routeway a battle might occur on with ease and strategic advantage, and furthermore at 40m high it probably counts as a hill (though not a mountain in itself). On the downside, there is no obvious tomb on the hill. If, however, the Latin Mons of our description is translated "Mountain" (as opposed to "Huge Rock" for example), we have a wider set of possibilities, including the apparently man-made mound at Banc Cil-maen-llywd and other locations on the massif. In short, Banc-y-Warren and/or the Banc Cil-maen-llywd tumulus seem likely (there is actually a fourth tumulus on the back of the massif at Crug Farm*, just to add confusion over the term "Crug", however, this seems unlikely as a location).
Finally, there is also a Crug Mawr mountain in Powys, quite close to some of the other Wonders. Though there is a cairn on the top, and a stream a mile away called Nant-y-Bedd ["Stream/Gorge of the Grave"] there is no particular evidence this is the site of the wonder.